Fix BOOL property getters/setters

Tweak the BOOL properties so they are all accessed the same way.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Fixes IPHONEAPP-692

Change favoritedRetailVenues to a lazily fetched property and make sure it is nil'd out after the loading operation completes (to force a refetch), otherwise the previously fetched objects end up in an undefined state (and weirdness starts happening).

Signed-off-by: Blake Skinner <bskinner@mit.edu>